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Manifest Destiny and Expansion: 1815–1887



Four interrelated historical developments occurred from 1815 to 1887 and played key roles in the growth of the United States. First was the rise of King Cotton in the South, sparked by the invention of the cotton gin. Cotton growing dominated the South's economy and created the plantation system that required large numbers of enslaved workers. Second was the popular belief in America's Manifest Destiny—that America had a duty and a divine blessing to expand and prosper. The third, the Mexican-American War, was motivated by the belief in Manifest Destiny. America's borders expanded to the Pacific Ocean as a result of the war. The fourth development was western migration. Thousands migrated to the West to seek riches in gold mining or to farm or trade. Clashes between newcomers and Native Americans occurred and ultimately made significant changes in the lives of Native Americans.

At A Glance

  • Eli Whitney's invention of the cotton gin in 1793 made it possible to process massive amounts of cotton in a relatively short period of time, helping to make cotton king of the cash crops.
  • Because the cotton gin could clean so much cotton, plantations grew, and so did the use of enslaved labor.
  • King Cotton dominated the South's economy, created the plantation system, and increased reliance on enslaved labor, causing further entrenchment of the institution in the Southern economy.
  • Manifest Destiny was the divine belief that the United States could and should extend to the Pacific Ocean and expand northward and southward.
  • After the Mexican-American War (1846–48) and less than 100 years after the American Revolution, the United States reached from the Atlantic to the Pacific coast.
  • After gaining its independence from Spain in 1821, Mexico took control of Spanish-conquered territories in the New World, which included Texas and Alta California.
  • In 1845 the United States annexed the Republic of Texas, a move that ultimately led to the Mexican-American War.
  • The 1848 Treaty of Guadalupe Hidalgo ended the Mexican-American War and granted the United States vast new territory west of the Mississippi.
  • The Gold Rush of 1848 and the Silver Rush of 1859 drew thousands of people from around the world to America's West.
  • Construction of the Transcontinental Railroad, completed in 1869, and passage of the Homestead Act in 1862 opened the West to more settlers. Together they illustrate the active role of the federal government in promoting westward expansion.
  • More and more settlers arrived in the West, displacing Native Americans and reducing their access to traditional food sources.
  • Great Plains Indians had an established lifestyle and culture prior to westward expansion.
  • From the mid-19th century, the Plains Indians and the U.S. government fought each other for control of the Great Plains.